Insulating glass units (IGUs) are typically composed of two parallel glass panes spaced apart by a peripheral spacer. Spacers are typically made of metal, usually of tubular configuration, and are formed so as to have two flat sides that face the confronting surfaces of the glass panes. The spacers are bent so as to conform to the periphery of the glass panes. Typically, the spacers are adhered to the glass panes with a sealant that is gas-impermeable, such polyisobuytlene. An additional sealant, with strong adhesion force, such as silicone, is commonly applied around the outside edges of the IGU. For aesthetic purposes, muntins may be sandwiched between the panes to give the unit a divided light appearance. To improve thermal resistance across the glass assemblies, the space between the panes of glass, or interpane space, may be filled with an insulating gas such as argon. To perform adequately, the IGU must be filled with a proper amount of gas. Typically, the amount of gas flowed into the interpane space is gauged by flowing gas at a known rate for a specified period of time into the IGU.
Often, at least one pane surface of an insulating glass unit is coated with a low energy coating to prevent conduction of heat through the glass. These coatings can result in the reflectance of color from the glass surface. Typically, color reflectance is undesirable. Therefore, for aesthetic purposes, it is desirable to manufacture glass and IGUs that reflect at wavelengths in the blue or blue/green range.
In the manufacture of insulating glass units, uniform production lines are often used to produce large quantities of glass assemblies. In a typical production line, glass panes are transported to a conveyor with rollers on a vertical platen that transports the panes to a number of stations where various steps of the assembly process are performed.
In terms of quality assuring the reflected color of a IGU, for example, the methods have generally involved measuring the transmitted color of a coated glass pane before it is assembled into an IGU. Similarly, the gas fill concentration is typically quality controlled by procedures involving methods that destroy the IGU after the IGU has been fully assembled and removed from the production line. Therefore, materials are wasted and each unit cannot be quality assured.
It would be desirable therefore, to provide a quality control method that is capable of quality assuring each IGU produced in a non-destructive manner. Furthermore, to reduce costs, it would be desirable to provide an automated or semi-automated system on a production line that can quickly and accurately quality assure IGUs as they are manufactured without sacrificing materials, time, and labor expenses.